This invention relates to an implantable device and in particular, to a vascular access device that is implanted subcutaneously. Within the prior art, a variety of implantable access devices are known and have been brought to the point of commercial acceptance. Typical of the commercially available devices is the INFUSAID Infus-a-Port TM. This device comprises, in its most basic form, an implantable port having access via a septum at a perpendicular angle to the skin via a needle. It has coupled to it a purcutaneous catheter extending generally at a right angle to the direction of needle access to the ports' inlet. These implantable devices typically use a variety of materials typically plastic such as PVC, Teflon (polytetrafluoroethylene), polyethylene polypropolyne, polyurethane, polycarbonate, polythermalsulfane, polysulphone, polyolenfin, nylon and the like. Additionally, silicon, and rubber may be employed while special components can be made of stainless steel or titanium.
An example, of a self-sealing implantable body utilizing an integral housing is described in U.S. Pat. 4,543,088. As illustrated therein, fluid communication between the internal reservoir and catheter (not shown) is via a passageway. While the catheter is not illustrated, the '088 patent mentions the use of rigid connectors which can be incorporated in the fluid passageWay to provide attachment of catheters and tubing to the implanted port.
An example of such rigid connection is found in U.S. Pat. No. 4,673,394. As illustrated and described in that patent, an implantable drug dispensing reservoir employs a twist-lock catheter coupled to a bayonet type connection. That is the implantable port has a T-slot into which a metallic flanged fitting is fitted and rotated into a locking arrangement. The '394 patent also employs a tab which is sutured into place against the base plate of the port to prevent detachment of the twist-lock connector from the port body. Another example is the screw-in lock assembly of U.S. Pat. No. 4,569,675.
Examples of press couplings of catheters into implantable ports are illustrated in and described in U.S. Pat. Nos. 4,445,495; 4,692,146; 4,710,167; and 4,710,174. In each, press fitting by frictional contact is used to hold the catheter in place with the port body. In the '146 patent, a metal nipple or tube may be used to prevent inadvertent puncture of the catheter itself. U.S. Pat. No. 4,464,178. also directed to an implantable port having an outlet catheter and employs a retainer having a pair of ears which engage matching voids in the reservoir. Such provides a positive locking and prevents the catheter from disengaging. However, problems in manufacture and replacement of the catheter are inherent in such a scheme. Another alternative of frictional yet detachably mounting a catheter to an implantable device is found in U.S. Pat. No. 4,581,020 which employs a tapered fluid connector which frictionally fits into an inlet to allow the catheter assembly to be detached.
U.S. Pat. No. 4,704,103 employs a catheter coupling using a coaxial elastomer clamping member that is deformed as a pressure sleeve is screwed into the port. To prevent the clamping member from crushing the catheter, a rigid hollow support projects from the outlet bore and the catheter slides over it. Thus, fluid communication is maintained as the catheter is clamped into position. Such a system is difficult to assemble in situ and contains a large number of components requiring surgeon time and precision.
One of the difficulties with these various prior art techniques is that they are difficult to engage, that is that the catheter is difficult to engage to the implanted port during an implantation procedure. That is, the implantation of such a drug delivery device should be as simple as possible to minimize patient trauma and the degree of skill required by the surgeon. In general, the reservoir is implanted subcutaneously at a location in the body cavity of the patient to provide needle access for infusion of medication. The catheter is then placed having one end at the drug delivery site with the second end to then be attached to the port. Given limited space, devices which require twist lock fittings and the like are difficult to connect in vivo and utilize in practice.
Moreover, in many of the devices which simply fit by means of pressure fitting, friction or the like, there is no indication that a complete and positive connection has been made. That is, no audible or tactile reference occurs indicating that an acceptable connection between the catheter and the port has been achieved. During the implantation procedure the surgeon must visually check or pull to determine whether the components have been coupled. Finally, devices which utilize machined parts and the like are more expensive to manufacture, have problems of material incompatibility, and present, to varying degrees, the problems of patient discomfort.
An overriding consideration is that the connection, in addition to providing the above requirements, establishes a fluid tight coupling between the catheter and the implantable reservoir.